Does Coffee Dehydrate? Stunt Growth? 8 Important Coffee Questions, Answered

You may guzzle coffee every day, but do you know how exactly it affects your health? Experts weigh in on the role coffee plays in weight loss, disease, and more.

Will I get dehydrated from drinking coffee?

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This is the biggest coffee myth, experts agree. When British researchers studied the body fluid levels of 50 men, they were the same whether the men drank coffee or water for hydration. “We tell people to drink eight 8-oz cups of fluid per day, and we always thought you couldn’t include coffee,” says Halle Saperstein, RD, of Henry Ford West Bloomfield Hospital in Michigan. “But now studies show otherwise. It’s OK to count coffee as part of your fluid intake.”

So why the myth? “Caffeine is a natural diuretic, but the amount that you urinate is not as significant as we once believed,” says Saperstein. Still, since too much caffeinated coffee can make you jittery, water is probably the best form of hydration. Drink coffee in the morning, and use plain H20 for fluid intake the rest of the day.

Will coffee help me lose weight?

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Caffeine, a stimulant, is often used in weight loss pills, and a cup of coffee may result in a short-term rise in your metabolic rate. Still, there’s no proof that coffee can help you lose weight, says Saperstein. Plus, people tend to drink coffee with calorie-packed creams and sugars. Saperstein’s suggestion: Use skim milk, drink plain coffee instead of lattes (so you drink more coffee than milk), and limit the amount of sugar you use or opt for a 0-calorie sweetener.

Is coffee connected to cancer?

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When cancer patients visit Lindsay Malone, RD, at Cleveland Clinic, they often tell her they’ve cut out coffee because they assume it’s unhealthy. Coffee, however, is on the list of cancer-fighting foods published by the American Institute for Cancer Research because of its high antioxidant content. “Cancer starts with DNA damage,” says Malone. “The antioxidants in coffee protect your cells and keep them healthy. If you have any DNA damage from, say, secondhand smoke or environmental pollutants, antioxidants can help repair cell damage.” Various studies have linked coffee to decreased risk of liver, breast, prostate, and melanoma skin cancers, among others.

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Is coffee bad for my heart?

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For most healthy people, caffeine can cause a short, temporary increase in blood pressure, but isn’t harmful in the long run. “Avid coffee drinkers can build up a tolerance to the caffeine and may not experience such effects after a cup,” says Leigh Tracy, RD, LDN, of Mercy Medical Center. People with high blood pressure, however, should talk to a doctor to see whether they should limit caffeine. “Those with high blood pressure should pay particular attention to how they feel when they drink coffee,” says Jennifer Powell Weddig, RDN, a professor of nutrition at Metropolitan State University of Denver. “They may find that their heart rate gets faster or notice palpitations.”

Does coffee raise cholesterol levels?

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Cafestol, a compound in coffee, is a potential stimulator of increased LDL cholesterol. “The catch is, it’s found in the oily portion of coffee,” says Weddig. “If you use a paper filter to make your coffee instead of something like a French Press, you lose that component.” Mesh filters, like those in a French press, will not eliminate the cafestol. However, if you don’t already have elevated LDL cholesterol, you likely don’t need to be concerned, says Weddig.  

Will coffee cure a hangover?

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If you’re feeling groggy after an eventful night, coffee might help. “If you didn’t get high-quality sleep, which contributes to a hangover, coffee will stimulate the central nervous system and improve focus,” says Malone. It doesn’t, however, clear out the alcohol in your system, so skip the end-of-the-night cup of coffee. It won’t help you sober up.

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Does coffee cause women's breasts to shrink?

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A study published in the British Journal of Cancer found that women who drank three or more cups of coffee daily had breasts that were 17 percent smaller than those who drank less coffee. Each additional cup increased effects. Researchers say too much caffeine can affect hormones, which impacts breast size. Still, it’s an “all-things-in-moderation” situation. “They will get smaller,” lead researcher Helena Jernström of Lund University in Sweden told The Telegraph. “But the breasts aren’t just going to disappear.”

Does coffee stunt growth?

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It’s what your mother told you when you wanted a sip, but there’s no truth to the idea that coffee or caffeine stunt growth, says Malone. “There is some research that caffeine can leach calcium from the bones, but older adults seem to be more susceptible to that than younger populations,” she says. The amount is so small, however, that slightly increasing milk intake can make up for the loss in calcium. The calcium-leaching effect of one cup of coffee can be balanced with two tablespoons of milk.

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